"WriteRoom for the iPhone and iPod touch can save that idea (and perhaps, by extension, the world). You might be familiar with the mobile app's big sibling, the Mac text editor by Hog Bay Software which shares the same name. WriteRoom for the Mac is famous for having a fullscreen interface which minimizes distractions and helps you focus on writing. Unlike with Mac programs, though, every iPhone app is presented in 'fullscreen mode,' so WriteRoom for the iPhone can't rest on its big brother's big feature to stand out in the crowded iPhone text-editing field.
If you find yourself using your iPhone as a replacement for your ideas notebook and don't care for the device's included Notes app, WriteRoom is well worth its £3 price tag for the ease of copying documents to and from your iPhone (and doubly so if you plan on buying another of Hog Bay Software's apps, because you get a coupon with WriteRoom for the iPhone that is good for £3 off the price of either WriteRoom for the Mac or Taskpaper)."